This invention relates generally to semiconductor integrated circuit packaging and more particularly, it relates to a pin grid array integrated circuit package which has an improved electrical connection means for providing electrical interconnection between terminal pads at the outer ends of a metalized trace pattern formed on a plastic tape circuit and terminal pin ends located on a package substrate.
Due to the increasing commercial need for high density packaging for large scale integration (LSI devices), there has been developed in the industry a common arrangement referred to in the art as a pin grid array (PGA) integrated circuit package. The PGA integrated circuit package includes generally a package substrate having a rectangular or square configuration. A plurality of metal terminal pins extend outwardly from the bottom surface of the package substrate and may protrude slightly above the top surface thereof. The integrated circuit package varies in size dependent upon the number of terminal pins which could be between 68 to 410. The plurality of terminal pins are disposed in the form of rows and columns so as to provide a matrix array.
In order to provide electrical connection between the semiconductor chip or die and terminal pins of the package substrate, the PGA integrated circuit package typically also includes a plastic tape circuit havinga metalized trace pattern formed on its bottom surface. The metalized trace pattern is comprised of a plurality of spaced apart conductive leads terminating at their outer ends with spaced apart metal terminal pads. The terminal pads are located in alignment or registration with the slightly protruding terminal pin ends of the package substrate. Permanent mechanical joinder between the terminal pads and terminal pin ends has been effected heretofore by a number of conventional metallurgical bonding procedures such as laser welding, ultrasonic welding, or the like on automatic equipment.
As the number of terminal pins on the PGA integrated circuit package grows, the cost of the automatic equipment required to perform such metallurgical bonding procedure is also increased. Further, in order to provide reliable bonding connections there is required a precise alignment of the terminal pads to the corresponding slightly protruding terminal pin ends. In view of the high number of terminal pads to be bonded, there is an increased possibility that at least one or more of the bonding connections will be defective causing the assembled PGA package to be rejected. If the defective bonding connections are to be repaired, then there is required a major rework process and thus additional labor expanse is incurred thereby increasing manufacturing costs.
It is therefore believed what is needed is a pin grid array integrated circuit package which has an improved electrical connection means for providing electrical interconnection between the terminal pads and the terminal pin ends. The electrical connection means of the present invention comprises an electrically conductive elastomeric material which establishes electrical interconnection between the terminal pads and the corresponding metal terminal pin ends. As a result, the critical alignment of the terminal pads and terminal pin ends has been eliminated. Further, in the event of a defective component, the repair and/or replacement of components in the instant PGA chip package has been made easier and more simplified.